1. Field of the Invention
The present invention relates to a magnetic transducer such as a magnetoresistive element, a thin film magnetic head and a method of manufacturing the same. More particularly, the present invention relates to a magnetic transducer comprising a magnetic domain control film to suppress, for example, Barkhausen noise or the like, a thin film magnetic head and a method of manufacturing the same.
2. Description of the Related Art
Recently, an improvement in performance of a thin film magnetic head has been sought in accordance with an increase in a surface recording density of a hard disk drive. A composite thin film magnetic head, which has a stacked structure comprising a reproducing head having a magnetoresistive element (hereinafter also referred to as an MR element) and a recording head having an inductive-type magnetic transducer, is widely used as a thin film magnetic head.
MR elements include an AMR element using a magnetic film (an AMR film) exhibiting an anisotropic magnetoresistive effect (an AMR effect), a GMR element using a magnetic film (a GMR film) exhibiting a giant magnetoresistive effect (a GMR effect), and so on.
The reproducing head using the AMR element is called an AMR head or simply an MR head, and the reproducing head using the GMR element is called a GMR head. The AMR head is used as the reproducing head whose surface recording density exceeds 1 gigabit per square inch (0.155 gigabits per square centimeters), and the GMR head is used as the reproducing head whose surface recording density exceeds 3 gigabits per square inch (0.465 gigabits per square centimeters).
As the GMR film, a xe2x80x9cmulti-layered type (antiferromagnetic type)xe2x80x9d film, an xe2x80x9cinductive ferromagnetic typexe2x80x9d film, a xe2x80x9cgranular typexe2x80x9d film, a xe2x80x9cspin valve typexe2x80x9d film and the like are proposed. Of these types of films, the spin valve type GMR film is most efficient as the GMR film which is relatively simple in structure, exhibits a great change in resistance in a low magnetic field, and is suitable for mass-production.
FIG. 20 is a sectional view of the magnetoresistive element, which uses a spin valve type GMR film (hereinafter referred to as a spin valve film) disclosed in Unexamined Patent Application Publication No. Hei 8-45032, parallel to the opposed face (medium-facing surface or air bearing surface; ABS) to a magnetic recording medium. The magnetoresistive element has the stacked structure comprising a free layer 63 made of a soft magnetic material, a spacer layer 65 made of a nonmagnetic metal, a pinned layer 70 made of a ferromagnetic material and an antiferromagnetic layer 66 made of an antiferromagnetic material in the order named on an underlayer 62 made of Ta (tantalum) or the like. The antiferromagnetic layer 66 is covered with a protective layer 67. Exchange coupling is induced on an interface between the pinned layer 70 and the antiferromagnetic layer 66, and thus the orientation of the magnetization of the pinned layer 70 is fixed in a direction indicated by 71 in the drawing, for instance. On the other hand, the orientation of the magnetization of the free layer 63 is freely changed in accordance with a signal magnetic field from a magnetic recording medium because the free layer 63 is isolated from the antiferromagnetic layer 66 by the spacer layer 65.
Reproducing of information using such a spin valve film, that is, the detection of a signal magnetic field from a magnetic recording medium is performed as follows. A detecting current (sense current) as a direct constant current is fed through the free layer 63 through lead electrode layers 92a and 92b in the direction indicated by 64 in the drawing, for example. Receiving the signal magnetic field from the magnetic recording medium rotates the magnetization of the free layer 63. The current passing through the free layer 63 is subjected to the resistance in accordance with a relative angle between the orientation of the magnetization of the free layer 63 and the fixed orientation of the magnetization of the pinned layer 70 and thus the resistance is detected as a voltage.
In such a magnetoresistive element, it is considered to apply a bias magnetic field to the free layer 63 to reduce Barkhausen noise. The Barkhausen noise is caused when many magnetic domains having random orientations of magnetizations change to one large magnetic domain, that is, change to a single magnetic domain, having a common orientation of magnetization under the influence of an external magnetic field.
Providing a magnetic domain control film produces the bias magnetic field. The magnetic domain control film is consisted of two layers of magnetic domain control ferromagnetic films 90a and 90b formed to sandwich the free layer 63 and of magnetic domain control antiferromagnetic films 90a and 90b deposited thereon, respectively. The orientation of the magnetizations of the domain control ferromagnetic films 90a and 90b is fixed by exchange coupling on each interface between the magnetic domain control ferromagnetic film 90a and the magnetic domain control antiferromagnetic film 90a, and the magnetic domain control ferromagnetic film 90b and the magnetic domain control antiferromagnetic film 90b in the direction indicated by 90c in the drawing. The bias magnetic field indicated by 64 in the drawing is applied to the free layer 63 sandwiched between the magnetic domain control ferromagnetic films 90a and 90b. The bias magnetic field flows to the same direction as sense current and is called as a xe2x80x9clongitudinal biasxe2x80x9d.
The explanation of magnetostriction of the magnetic domain control ferromagnetic films 90a and 90b will be made here. FIG. 21 simply illustrates the orientation of the magnetizations of the magnetic domain control ferromagnetic films 90a and 90b and a bias magnetic field applied to the free layer 63 as seen from above of the magnetoresistive element (the direction indicated by the arrow XXI in FIG. 20). The face indicated by reference character S in the drawing is a medium-facing surface opposite to the magnetic recording medium.
The magnetoresistive element is overlaid on the shield layer (not shown) or the like to make the reproducing head. It is known that the tensile stress F is applied on such reproducing head in the direction orthogonal to the medium-facing surface S. At this time, xe2x80x9ctensile strainxe2x80x9d (strain in the direction of the expansion Exp) parallel to the tensile stress F and xe2x80x9ccompression strainxe2x80x9d (strain in the direction of the compression Com) perpendicular to the tensile stress F are developed in the magnetic transducer. If the magnetostrictios xcexs of the magnetic domain control ferromagnetic films 90a and 90b is positive, the magnetization thereof may orient the same direction as tensile strain. That is, the magnetization of the magnetic domain control ferromagnetic films 90a and 90b rotates toward the tensile direction as indicated by dashed lines in the drawing. In this case, the bias magnetic field produced in the free layer 63 is weakened by the rotation of the magnetic domain control ferromagnetic films 90a and 90b. 
Unexamined Patent Application Publication No. Hei 6-84145 proposes that the magnetostriction xcexs of the magnetic domain control ferromagnetic film is a negative value having a large absolute value, specifically, xcexsxe2x89xa6xe2x88x9215xc3x9710xe2x88x926. If the magnetostriction xcexs of the magnetic domain control ferromagnetic film is negative, when the tensile stress F is applied to the magnetic domain control ferromagnetic films 90a and 90b as in FIG. 21, the magnetization thereof may orient to the direction of compression strain. In this case, the magnetic domain control ferromagnetic films 90a and 90b do not rotate and therefore the bias magnetic field produced in the free layer 63 is not weakened.
However, if the magnetostriction xcexs of the magnetic domain control ferromagnetic film is set to xcexsxe2x89xa6xe2x88x9215xc3x9710xe2x88x926, hysteresis in a change of the magnetizaion of the magnetic domain control ferromagnetic film for the external magnetic field increases. This results in instability in the output of magnetoresistive element.
Description is made by referring to FIGS. 22 and 23. FIGS. 22 and 23 illustrate the relation between the external magnetic field H and the magnetization M produced in the magnetic domain control ferromagnetic film. In FIG. 22, Hex indicates an exchange anisotropy magnetic field obtained by exchange coupling of the magnetic domain control ferromagnetic film to the magnetic domain control antiferromagnetic film. Hc indicates a coercive force of the magnetic domain control ferromagnetic film.
In general, the external magnetic field H applied to the magnetic domain control ferromagnetic film is assumed to be about 0 with the magnetoresistive element reproducing.
As an example shown in FIG. 22, if Hex is negative value and have a small hysteresis, that is, the coercive force Hc is small and the external magnetic field H is about 0 (a region E), the magnetization M is always positive value M1. If Hex is positive value, the magnetization M is negative value M2 in the region E.
On the other hand, in an example shown in FIG. 23, if hysteresis is large in a change of the magnetization M, that is, the coercive force Hc is large and the external magnetic field H is about 0 (the region E), the magnetization M of the magnetic domain control ferromagnetic film can take two values (M1 and M2). Namely, the magnetic domain control ferromagnetic film may change into either M1 or M2. As a result, the bias magnetization applied to the free layer may change into two values of M1 or M2 and thus the output of magnetic transducer may vary.
The present invention is designed to overcome the foregoing problems. It is an object of the invention to provide a magnetic transducer capable of suppressing a variation in output and obtaining an appropriate bias magnetic field, a thin film magnetic head, and a method of manufacturing the same.
A magnetic transducer of the present invention comprising a magneto-sensitive layer detecting an external magnetic field and a magnetic domain control film applying a bias magnetic field to the magneto-sensitive layer, the magnetic domain control film includes: a magnetic domain control ferromagnetic film made of a ferromagnetic material; and a magnetic domain control magnetization fix film for fixing the orientation of the magnetization of the magnetic domain control ferromagnetic film, wherein the magnetostriction xcexs of the magnetic domain control ferromagnetic film is within a range of xe2x88x9215xc3x9710xe2x88x926 less than xcexs less than 0.
In a magnetic transducer of the invention, the magnetostriction xcexs of the magnetic domain control ferromagnetic film is within a range of xe2x88x9215xc3x9710xe2x88x926 less than xcexs less than 0 so that hysteresis in a change of the magnetization of the magnetic domain control ferromagnetic film to an external magnetic field is relatively small. The magnetic domain control ferromagnetic film always shows a constant magnetization, that is, never has a plurality of magnetizations in operation of the magnetic transducer (for example, under an external magnetic field of about 0). As a result, the magnetic domain control film always applies the constant bias magnetic field to the magneto-sensitive layer and the output of the magneto-sensitive layer becomes stable.
In a magnetic transducer of the invention, the magnetic domain control ferromagnetic film may be made of NiFe containing within a range of 82 to 90% by weight of Ni. In the magnetic domain control ferromagnetic film fabricated using NiFe of such composition, the magnetostriction xcexs of a range of xe2x88x9215xc3x9710xe2x88x926 less than xcexs less than 0 can be obtained.
In a magnetic transducer of the invention, the magnetic domain control magnetization fix film may be made of an irregular base antiferromagnetic material. The irregular base antiferromagnetic material can induce an exchange anisotropy magnetic field to ferromagnetic materials without heat treatment. The magnetic domain control magnetization fix film made of an irregular base antiferromagnetic material induces an exchange anisotropy magnetic field on an interface between the magnetic domain control ferromagnetic film and the magnetic domain control magnetization fix film by stacking these two layers without heat treatment.
In a magnetic transducer of the invention, the magneto-sensitive layer may include a magneto-separative layer; a soft magnetic layer formed on one side of the magneto-separative layer, the orientation of magnetization of the soft magnetic layer being freely changed by an external magnetic field; a ferromagnetic layer formed on the other side of the magneto-separative layer; and an antiferromagnetic layer formed on the ferromagnetic layer on the side opposite to the magneto-separative layer.
In a magnetic transducer of the invention, a stack pattern includes the ferromagnetic layer, the magneto-separative layer and the soft magnetic layer may be formed on the antiferromagnetic layer and the magnetic domain control film may be formed laterally adjacent to the stack pattern on the antiferromagnetic layer. The contact area of the magneto-sensitive layer and the magnetic domain control film (only the contact area between the antiferromagnetic layer and the magnetic domain control film) is widened by forming the magnetic domain control film on the antiferromagnetic layer of the magneto-sensitive layer. Consequently, electrical contact resistance between the magneto-sensitive layer and the magnetic domain control film is reduced.
A thin film magnetic head of the invention comprises a magnetic transducer having a magneto-sensitive layer detecting an external magnetic field and a magnetic domain control film applying a bias magnetic field to the magneto-sensitive layer and the magnetic transducer may have any of the structure described above.
A method of manufacturing a magnetic transducer of the invention includes the steps of: stacking an antiferromagnetic layer, a ferromagnetic layer, a magneto-separative layer and a soft magnetic layer on a substrate in the order named; patterning the ferromagnetic layer, the magneto-separative layer and a soft magnetic layer to form a stack pattern including these three layers; and forming a magnetic domain control film including a magnetic film having the magnetostriction xcexs within a range of xe2x88x9215xc3x9710xe2x88x926 less than xcexs less than 0, laterally adjacent to the stack pattern on the antiferromagnetic layer. In this method, the structure that the stack pattern consisted of the ferromagnetic layer, the magneto-separative layer and the soft magnetic layer and the magnetic domain control film are formed on the antiferromagnetic layer.
In a method of manufacturing a thin film head of the invention, a thin film magnetic head comprises a magnetic transducer having a magneto-sensitive layer detecting an external magnetic field and a magnetic domain control film applying a bias magnetic field to the magneto-sensitive layer formed by the steps of: stacking an antiferromagnetic layer, a ferromagnetic layer, a magneto-separative layer and a soft magnetic layer on a substrate in the order named; patterning the ferromagnetic layer, the magneto-separative layer and a soft magnetic layer to form a stack pattern including these three layers; and forming a magnetic domain control film including a magnetic film having the magnetostriction xcexs within a range of xe2x88x9215xc3x9710xe2x88x926 less than xcexs less than 0, laterally adjacent to the stack pattern on the antiferromagnetic layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.